Electric-furnace control



Nov. 17, 1925. 1,562,204 R. CARLSTEDT ELECTRIC FURNACE CONTROL Filed June 24 1924 2 Sheets-Sheet 1 I fffiyna Qrlsidf 351, 3/ ML PL Filed June 24 1924 2 Sheets-Sheet 2 R CARLSTEDT ELECTRIC FURNACE CONTROL Nov. 17, 1925 gvwen'toz @1101 OF/$15 0 f whim Patented Na. 17, 1925.

UNITED STATES RAGNAR onnnsrn n'r, or STOCKHOLM, swniinn. ASSIGNOR r ARCA REGULATORS PATENT OFFICE. v

I INCORPORATED, A CORPORATION OF VIRGINIA.

ELECTRIC-FURNACE CONTROL.

Application filed June 24, 1924. Serial No. 722,046.

To all whom it may concern Beit known that I, RAGNAR CARLs'rEnT, a subject of the King of Sweden, and resident of Stockholm, Sweden, have invented certain new and useful Improvements in Electric Furnace Controls (for which I filed applications in Sweden May 27, 1920; Germany,

July 10, 1922; England, Apr. 5, 1923; Canada, June '7, 1922; and Japan, July 13, 1922), of which the following is a specification.

My invention relates to an automatic regulating mechanism for the electrodes of an electric furnace and has for its object to provide an automaticregulation which is extremely sensitive and yet not delicate; to regulate the electrodes so that a constant temperature is maintained inthe furnace and to regulate the electrodes both by amperage and voltage so that {under normal conditions the amperage is the controlling factor, moving the electrodes closer together This application 1s a continuation in partcopending application Serial No.

\ drawingsFig. 1 shows the invention applied to an electric furnace of the Rennerfelt ty e; p and Fig. 2" shows the same for lower values of amperage, while at low values of voltage the electrodes are pre-v vented from contacting.

Further objects will be evident as the description proceeds.

of my 563.458, filed May 24, 1922.

The accompanying drawmgs illustrate my invention diagrammatically in a manner which, taken in connection with the text. herewith, will enableone skilled in the art j to build and operate-the same, and in these Gronwall type offurnace.-,

In Fig. 1, 1O designates the electric furs nace which-is provided with three electrodes 11,- 12 and 13. Two of theseelectrodes, 11

andv 12, are regulated by means of similar v mechanisms so that only one need be demeans of a flexible member in two parts 14' scribed to give'a full and clear understanding of theinvention. V v a Electrode. 12 is shown as operated by and 15, "as, for example, a chain. Part 14 is fastened to the electrode as indicated aty16 and passes first-around pulleyblock 18, then around pulley block: 19,- thence around pulley block-20 and is, connected to. counterweight 21. Part 15 is cQnnected to the movable electrode as indicated. at' 17, passes" around jjwith two relays 36 and 37,

applied to t e y A actuation, through conduit 38 and branch pulley block 19, and is connected to piston rod 22 attached'to piston 23 in cylinder 24.

Cylinder 24, piston 23, piston rod 22, flexible members 14, 15, the counterweight 21 and the pulleys constitute what I term a servomotor. This is the primary actuating agent ,29 for liquid'under pressure or a discharge conduit 30 which carries liquid to waste.

Attached to the pilot valve-isa diaphragm 31 forming a part of the boundary of dia-' phragm chamber 32. Diaphragm chamber 32 is connected with supply conduit 29 by means of conduit33which has a restriction 34 therein. For purposes of description I have shown this conduit 33 as outside the main housing for the pilot valve but it is evident that this conduit with its restricted 7 portion may be within the said housing. It is sufficient that there is some .restricted means of supplying liquid to diaphragm chamber 32. It is not necessary that both the servo-motor and actuating means he sup,-

plied from the same source. Spring 35 acts on-the pilot valve in opposition to the pres sure in die hragm chamber 3 2.

The diap iragm chamber 32 communicates tertiary agents of.

conduits 39 and 40. The branch pipe 39 9 terminates: in a nozzle 41 through which a continuously. flowing stream of liquid passes, and branch pipe 40 terminates in a nozzle 42. Nozzle 41 is controlled by lever 43 pivoted at 44. An adjustable spring 45acts on the,

lever tending to force it against the nozzle 7 whereby to diminish :the flow of liquld;

therethrough; An electro-magnet 46 consisting of a core surrounded by a coil which is'connected to current, transformer 47 also acts on lever 43'by.its attractive effect on.

armature 48. By this'me'ans the lever 43 is moved in response to changes of current in the electric circuit 49' which srophes electric energy to the electrodes.

" nected across the wires of circuit 49 so that through.

it is responsive to voltage. At normal voltage magnet 50 holds lever 51, against nozzle 42 so that little or no' liquid discharges there- The relays: drain through conduits 52 and 53.

The mode of operation of the arrange ment is as follows: Spring 45 is adjusted to the correct value of amperage for the proper arc across the electrodes. If the resistance between the electrodes increases, due to consumption of the carbonof electrode 12, the strength of the current in circuit 45) decreases. This decreases the ,induced current 'in current transformer 47 and consequently in magnet 46 and he force of the magnet being decreased correspondingly, lever 43 moves closer to nozzle 41 under the preponderating action of spring 45'. The suppression of the jet flow through the nozzle increases the pressure in conduits 39,- 38 and consequently in diaphragm chamber 32. Increase of pressure in chamber 32 causes a movement of the pilot valve 27 to the left as shown in the drawing, thereby connecting conduit 25 with supply conduit 29' so that liquid under pressure is admitted to the servo-motor. Piston 23 is then moved down-v wardly causing electrode .12 to move inwardly toward electrode 13,by means of the flexible members and pulleys, whereby the resistance is decreased and the current in circuit 49, increased, thus returning the de vice to a state of balance.

If the current exceeds the normal value due,'for example to decreased resistance between the electrodes, magnet 46 increases in, strength of magnetic field and attracts the armature 48 so that the 'flow'thr'oughno'zzle -41 in increased which, in turn, decreases the pressure in conduits 39, 38 and-diaphragm J chamber 32. Decrease of pressure in cham- 27. to the right as shown in Fig. .1 whereby ber 32 causes movement ofthe pilot'valive conduit 25 is connected with discharge conduit 30. The counterweight 21 their over--- comes the-"liquid ressureineylinder 24 and movesthe electro e outwardly, thus increas-" ing the resistanoebetween the electrodes and causing a return equilibrium 7 The resistan .function otethe mperature inthe furnace so that changes in temperature react ion the evennessofheat'isobtained; I.

regulator in' such a manner, that}: an v exact 54 in relay is set to nozzle until a certain voltage 42 clo i 9! P half the: normal vo ta across the electrodes is a from nozzle 42, the pressure in diaphragm chamber 32 then depending only on the action of relay 36. If, however, the voltage in circuit 49 decreases to a low Value, relay 37 will be brought into operation and the forceof spring 54 will preponderate over the attractive force of magnet 50, causing lever 51 to increase the flow through conduit '40. This decreases the pressure in chamber 32, thus causing connection between the servo-motor and discharge conduit 3O whereby the electrodes are-moved apart. Suppose, for example, the power in circuit 49 should suddenly cease. The consequent drop in amperage would cause the electrodes to move together and, if nothing prevented it,"they would hit, causing injury to the electrodes. However the low voltage is responded to by relay 37 which operates, as above explained, to move the electrodes apart. This relay thus prevents short circuiting when the current. is cut in.

In similar manner electrode 11 iscontrolled by a normally operating relay and a safety low voltage relay which operate on an actuating. means, in turn controlling a servo-motor.

In starting the furnace it is'merelynecessary to throw in the main switch and there will. be a sufiicent voltage drop across the terminals of electro-magnet 50 to attract lever 51- and prevent outflow through nozzle 42. Since the amperage is'then zero or very -low, there is little or no outflow of liquid through nozzle 41, and thus the electrodes are brought together until the desired'cun rent in the arc 1s obtained.

My invention has been applied in practice with unusual results. .7 The current is kept so constant that a movement of the pointer of the meter is barely susceptible. .In one installation the production has been in,

'nace 61 with a modified arrangement of connecting up the servo-motor to' provide a relatively smaller cylinder for'these" larger furnaces. a3

The electrode is moved into and out of the furnace by means of a chain or the like passing around pulley 63 connected with counterweight .64 which vis-heavier than the electrode. A-seeond chain or similar flexible memberpassee'over pulleys 62 and 63 and is also connectedto eou'nter'weight64. This member 59 is connected at the opposite end to piston rod 66 which is. attached to piston 67 movable in cylinder 68-due to, the pressure of li hid in the cylinder.-

The w 'ole cylinder. '68.- is mow b1? means of a chain or the like 69 wound around a drum 7(), which drum is adapted to be rotated by means of a Worm-wheel, worm and handwheel indicated at 71. Thus as the electrode is burnt and it recedes into the furnace the hand adjustment 71 may 'be used to take care of the greater movement of the chain 59 while the servo-motor cylinder takes care of the momentary fluctuations. This provides a simple flexible arrangement and avoids large heavy and cu n'lbersome appa-ratus.

The cylinder 68 is connected up to a secondary and tertiary agent of force impulse transmission in a manner similar to that of Fig. 1; A part'o'f conduit 25 is flexible.

In operation: Suppose the hand adjustment 71 is set so that the piston ()7 is approximately in the middle of cylinder68. Suppose now the resistance across the furnace arc increases. The decreased current in circuit 49 causes asmovement of lever 43 toward nozzle 41 due to the decreased magnetic field in magnet 46. This increases the pressure in chamber 32 which causes a movement of the pilot valve 27 to connect cylinder 6 8 with supply conduit 29, thereby increasing the pressure in cylinder68. This causes amovement of the electrode 60 into the furnace against the action of counterweight 64, thus decreasing the arc resistance and returning the parts to a state of equilibrmm.

The reverse operation and the function of low voltage relay 37 will be readily under-,

stood from an examination of the drawing taken in connection with the description and showing of Fig' 1.

It is to be noted that in each form of the invention the parts are so arranged that should anything happen to cause a failure of the liquid pressure as, for example, a

break in connecting conduit 25, the movable electrodes will be withdrawn from the furnace and contact between them is prevented. It is' evident that in Fig. 2 cylinder 68 might be inserted in that part of flexible member 73 which is just above electrode 60. Many similar changes in the construction and arrangement of parts may obviously be made without departing from the spirit or scope of the invention. In certain cases the secondary agency which it have termed an actuating means may be omitted.

Although there are several intermediate agencies of control, my apparatus is extremely sensitive and yet it can be made without delicate parts subject to; wear and liability to become disadjusted. The sensitiveness is due primarily to the use of a liquid and the manner of utilizing the liquid in a continuousl flowing stream and the combination of t e continuous stream with the other parts herein set forth in a manner such that minute changes ofthe actuating impulse cause exact, definite and instantaneous changes in a series of-progressively increased liquid forces which are multiplied to give an enormous primary actuating force for that which is to be controlled. r

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is:

1; Electric furnace apparatus comprising, in combination, an electrode, an electric circuit for said electrode, a liquid pressure 0perated servo-motor to dontrol said electrode, a nozzle through which a stream of liquid flows continuously, a lever controlling flow through said nozzle, means whereby changes of pressure in said stream of liquid caused by movement of said lever cause operation of a said servo-motor, and means respons ve toamperage in said circuit to control movement of said lever.

2. Electric furnace apparatuscomprising, in combination, an electrode, an electric circuit for said electrode, a liquid pressure operated servo-motor to control said electrode, a nozzle through which a stream of liquid flows continuously, a lever controlling flow through said nozzle, means whereby changes of pressure in saidstream 9f liquid caused by movement of said lever cause operation of said servo-motor, an armature on said lever, and a solenoid responsive to amperage in sa d circuit to change the position of said armature.

3. Electric furnace apparatuscomprising, in combination, an electrode an electric circuit for said electrode, a liquid pressure operated servo-motor to 'control said electrode, a nozzle through which a stream of liquid flows continuously, a lever controlling flow through said nozzle, means whereby changes of pressure in said stream of liquid caused by movement of said lever cause operation of said servo-motoiyme'ans responsive to amperage-in said circuitto control movement,

of said lever, a second nozzle through which a stream of liquid flows continuously, a second lever controlling flow through the secondnozzle, means whereby changes of pressure in the last mentioned stream of liquid cause operation of said servo-motor and,

Nil

llil

ment of said electrode, and means responsive to amperage and voltage in said circuit to controlsaid liquid pressure operated means, said means operatlng to move said electrodes together upon decrease of amperage in normal operation, and to move said electrodes apart when the voltageis extremely low. 7 U

5. In combination, an electric furnace, an

electrode for said furnace, a liquid pressure 339 i operated servo-motor to control said electrode, an electric circuit for said electrode, a,

continually flowing stream of liquid to indirectly control said liquid pressure operated servo-motor and means responsive to conditions in said electric circuit to control said trodes for said furnace, automatic means to move said electrodes together upon decrease of amperage and to move sa1d electrodes apart when the voltage is zero.

" 8. In combination, an electric furnace, an

electrode for said furnace, liquid pressure operated means to control said electrode. means responsive to amperage to control said liquid pressure, operated means under normal conditions of operation and means responsive to voltage to control said electrode under extreme conditions.

9. In combination, an electric furnace, an electrode for said furnace, a liquid pressure operated servo-motor to control. said electrode, liquid pressure operated actuating means to control said servo-motor, a relay electric circuit for said electrode and means I responsive to electric impulses in said circuit to control said relay. v

lO. In combination, an electric furnace, an electrodejor said furnace, a liquid pressure operated servo-motorto control said electrode, liquid pressure operated actuating means to control said'servo-motor, a relay comprising a continuously flowing stream of liquid to control said actuating means, an electric circuit for said electrode, means responsive to amlwrage in said circuit to control said relay and means responsive to voltage in said circuit to control said continuously flowing stream of liquid under low voltage conditions regardless of control in response to amperage.

11. Electric furnace apparatus comprising an electrode, a circuit for said electrode,

a liquid pressure operated servo-motor to move said electrode comprising a cylinder and a piston movable in said cylinder, a rolay'including a cont nuously flowing stream of liquid, changes of pressure in which are adapted to operate the servo-motor, means to control said stream of liquid in response to conditions in said 'eircuit, and means to move said cylinder by han -In testimony whereof I hereunto aflix my signature.

RAGNAR OARLSTEDT. 

